In French, one can say Je suis seul (I am alone) or Je me sens seul (I feel alone), but nothing as baldly distressing as “I am lonely” or “I am lonesome.”says Henry Cole in the New Yorker. Suggesting other lonely French words such as esseulé or délaissé would probably not change his mind, since they are arguably not an exact translation for lonely. Can one then say that there are words in one language without an identical counterpart in another language? As a second example, several people told me (with patriotic pride) that the Romanian dor cannot be translated in any other language. I have trouble seeing how it is substantially different from longing.
I believe this kind of affirmation (like many declarative sentences) can be read in a strong and a weak sense.